Most important Feynman diagrams

[QuantumCosmo]

Hi,
what do you think are the most important Feynman diagrams (or probably better: what do you think are the most important processes in particle physics)?
Thanks,
Quantum Cosmo

[Bill_K]

This is a pretty weird question, Cosmo. Like, what is your favorite nucleus?

[bapowell]

This is a pretty weird question, Cosmo. Like, what is your favorite nucleus?
That's easy. Radioactive calcium.

[Polyrhythmic]

Tadpoles, easily.

[PAllen]

Tadpoles, easily.

Ah, if only they had gone with the other name. The Journal where Coleman first published this rejected the name 'tadpoles' and insisted he change it. He sent back the alternative: 'spermions'. They accepted tadpoles.

[Simon_Tyler]

Penguin diagrams - they'd beat tadpoles in a fight any day of the week.
http://fliptomato.wordpress.com/2008/05/02/autographed-penguin-diagram/
http://en.wikipedia.org/wiki/Penguin_diagram

An attempt at a serious answer...

Tree level diagrams - since they dominate most effects.

Loop diagrams where new physics appears:
Eg 1-loop box diagram in QED that leads to photon-photon interactions.

Of course, one-loop is only semi-classical. I remember that some stuff first happens at two loops, but can't remember what it is off the top of my head.

[Polyrhythmic]

True, that beats tadpoles!

[jtbell]

I can think of a certain regular poster to PF whose favorite Feyman diagram is surely the penguin! :biggrin: